Abstract:

Background: The potential causes for variation in virulence between distinct M. tuberculosis strains are still not fully
known. However, differences in protein expression are probably an important factor. In this study we used a labelfree
quantitative proteomic approach to estimate differences in protein abundance between two closely related M.
tuberculosis strains; the virulent H37Rv strain and its attenuated counterpart H37Ra.
Results: We were able to identify more than 1700 proteins from both strains. As expected, the majority of the
identified proteins had similar relative abundance in the two strains. However, 29 membrane-associated proteins
were observed with a 5 or more fold difference in their relative abundance in one strain compared to the other.
Of note, 19 membrane- and lipo-proteins had higher abundance in H37Rv, while another 10 proteins had a higher
abundance in H37Ra. Interestingly, the possible protein-export membrane protein SecF (Rv2586c), and three ABCtransporter
proteins (Rv0933, Rv1273c and Rv1819c) were among the more abundant proteins in M. tuberculosis
H37Rv.
Conclusion: Our data suggests that the bacterial secretion system and the transmembrane transport system may
be important determinants of the ability of distinct M. tuberculosis strains to cause disease.